Yesterday, only 19 states had totally mandatory helmet laws. Today that number is 18. Michigan Governor Rick Snyder just signed into law a bill making helmet use optional in that state — with strings attached. Informally known as “Darwin’s Law,” the bill allows riders to choose whether or not to wear a helmet if they’re at least 21 years old, carry an additional $20,000 in medical insurance and have either held a license for at least two years or completed a safety course. You can practically hear the sound of watermelons exploding from here.

The new law comes after years of campaigning by local ABATE (American Bikers Aiming Toward Education) groups. Former governor Jennifer Granholm twice vetoed similar measures. Their chief argument appeared to be the ever-tantalizing prospect of tourism dollars. The thinking being that pirates flock to states where mandatory helmet use doesn’t impact their ability to wear jaunty eye patches or make it inconvenient to carry a shoulder-mounted parrot. Why motorcyclists would want to visit Michigan — a state as flat and corner-free as a dinner plate — escapes us.

That $20,000 in additional insurance is intended to offset the additional expense of dealing with injuries that helmet-free riding brings. In Nevada, a state also considering the repeal of its helmet law, again to chase tourism dollars, it’s estimated that the average cost of treating a helmeted motorcyclist is $96,700. Helmet-free crashees cost, on average, $112,500. One Nevada hospital had to write-off $45 million in unpaid treatment costs for motorcyclists in a single year.

What impact will the repeal have on fatalities? In 1999, when Florida still required helmets, 164 motorcyclists were killed. In 2000, when the helmet law was repealed, that number climbed to 241. That number increased to 532 by 2008. There’s no data on the numbers of non-fatal injuries in that state.

According to the Michigan Office of Highway Safety Planning, the repeal will result in at least 30 additional motorcycle fatalities per year, 127 more “incapacitating injuries” and $129 million in added economic costs to the state.

This old ad for Buell motorcycles makes the case for helmet use far more eloquently than we can.

Michigan State Police issued a memo to all officers formalizing enforcement guidelines:

- The law does not require a motorcycle operator to carry or present proof he or she has a motorcycle endorsement for at least two years or has successfully passed the motorcycle safety course.

- The law does not require a motorcycle operator or passenger to carry proof of the $20,000 security required to operate or ride a motorcycle without a helmet.

- Officers may not stop a motorcyclist for not wearing a helmet based on the possibility the operator or passenger may be in violation of the helmet law.

- Operators and passengers who violate the new law are responsible for a civil infraction.

ABATE argues that helmets have very little to do with motorcycle safety, instead stating that the key to safe riding, “lies in rider education, car driver awareness and license endorsement.”